Running Shoes

ABSTRACT

A running shoe comprises an upper and a midsole attached to the upper, the midsole having a front portion corresponding to a forefoot and a rear portion corresponding to a heel. The front portion of the midsole may have one or more notches which may increase the flexibility of the midsole. One or more flex grooves may extend through the midsole to similarly increase the flexibility of the midsole. A flex groove may be associated with a notch via a notch and a flex groove being associated with a channel. The flex groove may have void regions in which the flex groove extends entirely through the midsole to define a void therein. The void regions may increase the movability of forefoot pods defined by the relationship of flex grooves and how they may intersect each other and extend through each other.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent application Ser. No. 18/089,077 filed Dec. 27, 2022, pending, which relates to and claims the benefit of U.S. Provisional Application No. 63/295,628, filed Dec. 31, 2021, and entitled “RUNNING SHOES,” the entire disclosure of all of which are expressly incorporated by reference herein.

STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

Not Applicable

BACKGROUND

When running or walking barefoot on natural, earthen surfaces, the foot does some unique things that it does not as readily do when shod. Toes lift 20-40 degrees and metatarsal heads drop slightly in the swing phase of the gait cycle. The body's center of mass travels from the heel to the forefoot largely unimpeded and more quickly than when in a shoe. The forefoot also expands up to 20%, mostly laterally, as it becomes weighted upon contact with the ground. Unfortunately, the biomechanics of running and walking barefoot on earthen surfaces are largely overlooked in the design of running shoes, which must be cushioned for use on hard, flat, manmade surfaces like concrete and pavement. By inhibiting the natural functions of the foot, available running shoes limit the foot's performance and may even increase the risk of injury.

BRIEF SUMMARY

The present disclosure contemplates footwear for overcoming the above drawbacks associated with the related art. One aspect of the embodiments of the present disclosure is a running shoe comprising an upper and a midsole attached to the upper. The midsole may have a front portion corresponding to a forefoot and a rear portion corresponding to a heel. The front portion of the midsole may define a toe spring of at least 40 mm and a plurality of flex grooves. The plurality of flex grooves may include one or more horizontal flex grooves and one or more longitudinal flex grooves, the one or more horizontal flex grooves extending in a lateral to medial direction of the running shoe and allowing the front portion of the midsole to lie flat in response to application of less than 15 pounds of force against the toe spring, the one or more longitudinal flex grooves extending in a front to back direction of the running shoe. The rear portion of the midsole may have a flat bottom that is narrower than the upper in the lateral to medial direction of the running shoe.

The toe spring may be at least 50 mm. The one or more horizontal flex grooves may allow the front portion of the midsole to lie flat in response to application of less than 10 pounds of force against the toe spring, preferably less than 5 pounds of force. The one or more horizontal flex grooves may include a first lower flex groove extending into the front portion of the midsole from a bottom thereof and a first upper flex groove extending into the front portion of the midsole from a top thereof, the first upper flex groove being vertically aligned with the first lower flex groove so as to reduce a thickness of the midsole therebetween (e.g., to 20%-35% of a maximum thickness of the midsole, preferably 25%-30%). The one or more horizontal flex grooves may include a first flex groove and a second flex groove spaced from each other in the front to back direction of the running shoe. The one or more longitudinal flex grooves may include a first lower flex groove extending into the front portion of the midsole from a bottom thereof and a first upper flex groove extending into the front portion of the midsole from a top thereof, the first upper flex groove being vertically aligned with the first lower flex groove so as to reduce a thickness of the midsole therebetween (e.g., to 20%-35% of a maximum thickness of the midsole, preferably 25%-30%). The one or more longitudinal flex grooves may include a first flex groove and a second flex groove spaced from each other in the lateral to medial direction of the running shoe. The upper may comprise an elastic material.

The rear portion of the midsole may be rounded from the flat bottom thereof to the lateral and medial sides of the running shoe (e.g., according to one or more radii of curvature of mm). The flat bottom of the rear portion of the midsole may be rounded about a perimeter thereof.

The midsole may exhibit zero drop from the rear portion to the front portion thereof. A maximum width of the front portion of the midsole in the lateral to medial direction of the running shoe may be greater than 140% of a maximum width of the rear portion of the midsole in the lateral to medial direction of the running shoe.

The running shoe may comprise an outsole attached to the midsole.

Another aspect of the embodiments of the present disclosure is a running shoe comprising an upper and a sole unit attached to the upper. The sole unit may have a front portion corresponding to a forefoot and a rear portion corresponding to a heel. The front portion of the sole unit may define a toe spring of at least 40 mm and a plurality of flex grooves. The plurality of flex grooves may include one or more horizontal flex grooves and one or more longitudinal flex grooves, the one or more horizontal flex grooves extending in a lateral to medial direction of the running shoe and allowing the front portion of the sole unit to lie flat in response to application of less than 15 pounds of force against the toe spring, the one or more longitudinal flex grooves extending in a front to back direction of the running shoe. The rear portion of the sole unit may have a flat bottom that is narrower than the upper in the lateral to medial direction of the running shoe.

The toe spring may be at least 50 mm. The one or more horizontal flex grooves may allow the front portion of the sole unit to lie flat in response to application of less than 10 pounds of force against the toe spring, preferably less than 5 pounds of force. The one or more horizontal flex grooves may include a first lower flex groove extending into the front portion of the sole unit from a bottom thereof and a first upper flex groove extending into the front portion of the sole unit from a top thereof, the first upper flex groove being vertically aligned with the first lower flex groove so as to reduce a thickness of the sole unit therebetween (e.g., to 20%-35% of a maximum thickness of the sole unit, preferably 25%-30%). The one or more horizontal flex grooves may include a first flex groove and a second flex groove spaced from each other in the front to back direction of the running shoe. The one or more longitudinal flex grooves may include a first lower flex groove extending into the front portion of the sole unit from a bottom thereof and a first upper flex groove extending into the front portion of the sole unit from a top thereof, the first upper flex groove being vertically aligned with the first lower flex groove so as to reduce a thickness of the sole unit therebetween (e.g., to 20%-35% of a maximum thickness of the sole unit, preferably 25%-30%). The one or more longitudinal flex grooves may include a first flex groove and a second flex groove spaced from each other in the lateral to medial direction of the running shoe. The upper may comprise an elastic material.

The rear portion of the sole unit may be rounded from the flat bottom thereof to the lateral and medial sides of the running shoe (e.g., according to one or more radii of curvature of 15-25 mm). The flat bottom of the rear portion of the sole unit may be rounded about a perimeter thereof.

The sole unit may exhibit zero drop from the rear portion to the front portion thereof. A maximum width of the front portion of the sole unit in the lateral to medial direction of the running shoe may be greater than 140% of a maximum width of the rear portion of the sole unit in the lateral to medial direction of the running shoe.

The sole unit may comprise a midsole and an outsole.

Another aspect of the embodiments of the present disclosure is a running shoe having a unique midsole, the front portion of which may define one or more notches in a top rail of the sidewall of that midsole. The flex grooves may also extend through this unique midsole. Both of these features, the notches and the flex grooves, may be associated with one another via a channel in the midsole. Each of these channels may at least partially define one or more channel surfaces associated therewith. The channels may act as an indentation or a recess of the midsole that extend towards the wearer's foot, with the channel surfaces being the portions of the midsole within the indentation/recess of the channel. The channels and their channel surfaces can come in various geometries, ideally a rectangular geometry that has three channel surfaces.

These notches and flex grooves may enable the midsole to contract and expand about those notches and flex grooves, thus increasing the flexibility of the midsole and allowing it to lay more easily flat to the ground with less effort from a wearer. When the notches and flex grooves are associated with one another via a channel, the flexibility of the midsole may be improved even further.

The flex grooves of the midsole may have one or more void regions that define a void in the midsole and the flex grooves. The void regions may span one or more of the flex grooves, including both longitudinal and horizontal flex grooves. The void regions may be operative to increase the movability of forefoot pods; these forefoot pods may be defined by the relationship between flex grooves and how they may intersect each other at intersection points and may further extend through the intersection points.

Depending on the spatial relationship of the void regions with each of the forefoot pods, the void regions may increase the moveability of certain forefoot pods to a greater degree than the other forefoot pods. This is particularly beneficial when the forefoot pods of a running shoe corresponding to the 1^(st), 4^(th), and 5^(th) metatarsal heads are given extra vertical moveability, which allows for a more natural and comfortable movement of a wearer's foot.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the various embodiments disclosed herein will be better understood with respect to the following description and drawings, in which like numbers refer to like parts throughout, and in which:

FIG. 1 is a right side view of a running shoe for a right foot, showing a lateral (outer) side thereof;

FIG. 2 is a left side view of the running shoe, showing a medial (inner) side thereof;

FIG. 3 is another ride side view of the running shoe with the front of the shoe flexed downward;

FIG. 4 is a bottom view of the running shoe;

FIG. 5 is a top view of a midsole of the shoe;

FIG. 6 is a cross-sectional view taken along the line 6-6 in FIG. 5 ;

FIG. 7 is a cross-sectional view taken along the line 7-7 in FIG. 5 ;

FIG. 8 is a cross-sectional view taken along the line 8-8 in FIG. 5 ;

FIG. 9 is a right side view of another running shoe for a right foot, showing a lateral (outer) side thereof;

FIG. 10 is a left side view of the running shoe of FIG. 9 , showing a medial (inner) side thereof;

FIG. 11 is a front view of the midsole of the running shoe of FIG. 9 ;

FIG. 12 is another right side view of the running shoe of FIG. 9 with the upper of the shoe outlined in dotted lines;

FIG. 13 is a bottom view of the running shoe of FIG. 9 ;

FIG. 14 is a top view of a midsole of the running shoe of FIG. 9 ;

FIG. 15 is a cross-sectional view taken along the line 15-15 in FIG. 14 ; and

FIG. 16 is a cross-sectional view taken along the line 16-16 in FIG. 14 .

DETAILED DESCRIPTION

The present disclosure encompasses various embodiments of footwear and, in particular, running shoes. The detailed description set forth below in connection with the appended drawings is intended as a description of several currently contemplated embodiments and is not intended to represent the only form in which the disclosed invention may be developed or utilized. The description sets forth the functions and features in connection with the illustrated embodiments. It is to be understood, however, that the same or equivalent functions may be accomplished by different embodiments that are also intended to be encompassed within the scope of the present disclosure. It is further understood that the use of relational terms such as first and second and the like are used solely to distinguish one from another entity without necessarily requiring or implying any actual such relationship or order between such entities.

FIGS. 1-8 are views of a running shoe 100 for a right foot, while FIGS. 9-16 are views of another running shoe 200, also for a right foot, that incorporates additional features that may replace and/or be combined with the features of the running shoe 100. While not separately illustrated, the running shoe 100, 200 may also be symmetrically designed for a left foot. The resulting pair of running shoes 100, 200 may be worn for running or walking on ordinary running surfaces, including roads and sidewalks, while advantageously allowing and encouraging the biomechanics and sensations of running or walking barefoot on natural, earthen surfaces, thus enhancing performance and reducing the risk of injury. The running shoe 100, 200 may generally include an upper 110 (e.g., vamp, quarter, etc.) and a sole unit, with the sole unit typically comprising a midsole 120, 220 and an outsole 130, 230. The midsole 120, 220 may be attached to the upper 110 and provide cushioning to absorb the shock of running on hard surfaces and may be made of ethylene vinyl acetate (EVA), for example, while the outsole 130, 230 may be a thinner, rubber portion of the sole unit that may be attached to the bottom of the midsole 120, 220 and patterned to provide traction. Advantageously, the sole unit, and particularly the midsole 120, 220, may be uniquely designed both in a front portion 122, 222 and a rear portion 124, 224 thereof (see FIGS. 3, 4 and 13 ) to promote the natural barefoot action of the wearer's foot without sacrificing the protective cushioning of the running shoe 100, 200. The running shoe 100, 200 may be configured such that an insertable insole (not depicted) can be coupled with the running shoe 100, 200. The insole may be coupled with at least a portion of the top surface of the midsole 120, 220 such that the bottom of the foot of a wearer may rest on the insole while they wear the shoe 100, 200. In this respect, the insole may be constructed and configured similarly to those conventionally used and known by those skilled in the art.

Referring to FIGS. 1-3 , the front portion 122 of the midsole 120, corresponding to a forefoot of the wearer, may define a toe spring H (see FIG. 3 ) that is great enough to allow and encourage the toes' natural vertical extension of 20-40 degrees relative to the rest of the foot during the swing phase of the gait cycle. (The relaxed “toe-up” position is shown with broken lines in FIG. 3 .) For a standard U.S. men's size 9D, for example, the toe spring H may be 40 mm or more (e.g., 40-60 mm), preferably at least 50 mm (e.g., 55 mm), and even more preferably at least 60 mm, as measured vertically from the ground to the foremost point 123 on the bottom of the shoe 100 (i.e., the farthest forward point that contacts the ground). For other shoe sizes, the toe spring H, as well as any other absolute measurements (e.g., millimeter measurements) described herein, may be proportionally greater or less according to conventional shoe sizing algorithms. It is also contemplated that the toe spring H may be described as an angle of elevation to the foremost point 123 (while the shoe 100 is in the relaxed “toe-up” position) as observed from the farthest forward point on the shoe 100 that contacts the ground during the “toe-up” position (indicated with reference number 125 in FIG. 3 ), which may be 25-40 degrees, for example. Unlike the rigid toe spring features of conventional running shoes, the front portion 122 of the midsole 120 may be flexible enough to be made to lie flat as shown in FIG. 3 easily and without substantial effort, such that the weight of the wearer's foot while running may naturally produce the flexed downward state shown in FIG. 3 during each stride. In this regard, the front portion 122 of the midsole 120 may be made to lie flat in response to application of less than 15 pounds of force against the toe spring H (e.g., normal to the top of the midsole 120 or sockliner), preferably less than 10 pounds of force or even less than 5 pounds of force.

The midsole 120 may preferably exhibit zero mm of drop from the rear portion 124 to the front portion 122 thereof while the running shoe 100 is worn flat against the ground (with the toes lying flat as described above), where drop may refer to the difference in height of the midsole between the rear of the foot and the ball of the foot. Preferably, the midsole 120 may exhibit zero drop from the rear portion 124 all the way to the foremost point 123 described above, rather than merely to the ball of the wearer's foot, where drop is typically measured to, for example. As a result, the toes, when the shoe sits or becomes weighted in the toes-flattened position, are able to exert pressure against a solid surface and initiate additional stabilization of the foot sooner in the gait cycle and when standing, just as the foot would if barefoot and not in a shoe. In the case of a conventional, cushioned shoe (where the cushioning is comprised of a midsole height greater than 10-15 mm and where that height tapers from near the ball of the foot to the tip of the shoe), the toes are unable to exert pressure against a solid surface until the very end of the foot's ground contact time, when the foot rolls over the toes and it is too late to initiate significant additional stabilization forces through the toes. The unique combination of previously described forefoot flexibility, combined with a significantly cushioned midsole of at least 10-15 mm of height and possessing zero drop as measured from the heal to the tips of the toes, may allow the shod foot to operate as effectively on concrete and pavement as the bare foot would on earthen surfaces.

Flexibility of the front portion 122 of the midsole 120 may be achieved, at least in part, by the inclusion therein of a plurality of flex grooves 126 a, 126 b, 127 a, 127 b (see FIGS. 4-7 ). In particular, one or more horizontal flex grooves 126 a, 126 b may provide the flexibility to allow the front portion 122 of the midsole 120 to easily lie flat as shown in FIG. 3 . The one or more horizontal flex grooves 126 a, 126 b may span the width of the midsole 120 in the front portion 122 thereof. Referring to FIGS. 4-6 , the one or more horizontal flex grooves 126 a, 126 b may include a first lower flex groove 126 a-1 extending into the front portion 122 of the midsole 120 from a bottom thereof and a first upper flex groove 126 a-2 extending into the front portion of the midsole from a top thereof, with the first upper flex groove 126 a-2 being vertically aligned with the first lower flex groove 126 a-1 so as to reduce a thickness of the midsole 120 therebetween (and thus promote flexibility near the base of the wearer's toes). The thickness of the midsole 120 may be reduced in this way to 20%-35% (preferably 25%-30%) of a maximum thickness of the midsole 120, for example. The reduced thickness may be 4-10 mm, for example, which may provide sufficient flexibility while still having enough structural integrity to be reliably formed by a conventional molding process and to not tear under normal walking and running conditions. Additional flexibility, and in particular a liveliness or springiness of the action of moving the front portion 122 of the midsole 120 between the two positions shown in FIG. 3 , may be provided by the material of the upper 110, which may be stretched over the midsole 120 and have built-in elasticity. In this regard, the upper 110 may comprise an elastic material such as a stretch knit fiber or one or more elasticated bungees sewn or otherwise affixed or embedded therein and attached to the midsole 120.

The one or more horizontal flex grooves 126 a, 126 b may include one or more horizontal flex grooves 126 a, 126 b spaced from each other in a front to back direction of the running shoe 100 (e.g., in a direction from the front 102 to the back 104 of the running shoe 100). In the illustrated example, two first horizontal flex grooves 126 a-1, 126 a-2 (lower and upper, respectively) promote flexibility near the base of the wearer's toes as described above, while two second horizontal flex grooves 126 b-1, 126 b-2 (lower and upper, respectively) are spaced therefrom so as to be farther back near the rearmost end of the front portion 122 of the midsole 120. These second horizontal flex grooves 126 b may similarly reduce the thickness of the midsole 120 therebetween (e.g., to 20%-35%, preferably 25%-30%, or 4-10 mm, for example) to promote flexibility of the midsole 120. The placement of the second horizontal flex grooves 126 b may, in addition to in some cases further improving the flexibility of the toe spring as described above, make it easier for the wearer to lift the rear portion 124 of the midsole 120 while the front portion 122 of the midsole 120 is still planted on the ground as the wearer pushes off the ground with each stride.

In addition to the one or more horizontal flex grooves 126 a, 126 b, the front portion 122 of the midsole 120 may further define one or more longitudinal flex grooves 127 a, 127 b that extend in the front to back direction of the running shoe 100 (see FIGS. 4, 5, and 7 ). The one or more longitudinal flex grooves 127 a, 127 b may span the length of the front portion 122 of the midsole 120 (e.g., from the front 102 of the shoe to the rearmost end of the front portion 122, typically between one-third and one-half of the way from the front 102 to the back 104 of the shoe 100). The one or more longitudinal flex grooves 127 a, 127 b may provide flexibility to allow the front portion 122 of the midsole 120 to bend independently at different locations in a lateral to medial direction of the running shoe 100 (e.g., in a direction from the lateral side 106 to the medial side 108 of the running shoe 100). In this way, the running shoe 100 may allow and encourage the natural biomechanics of the wearer's foot as 4th and 5th metatarsal heads drop earlier than the others during the wearer's stride and/or as 2nd and 3rd metatarsal heads drop earlier than the 1st metatarsal head.

The one or more longitudinal flex grooves 127 a, 127 b may include a first lower flex groove 127 a-1 extending into the front portion 122 of the midsole 120 from a bottom thereof and a first upper flex groove 127 a-2 extending into the front portion of the midsole from a top thereof, with the first upper flex groove 127 a-2 being vertically aligned with the first lower flex groove 127 a-1 so as to reduce a thickness of the midsole 120 therebetween (and thus promote flexibility between the wearer's 4th and 5th toes and the rest of the wearer's toes). The one or more longitudinal flex grooves 127 a, 127 b may further include, spaced apart from the first flex groove(s) 127 a-1, 127 a-2 in the lateral to medial direction of the running shoe 100, a second lower flex groove 127 b-1 extending into the front portion 122 of the midsole 120 from a bottom thereof and a second upper flex groove 127 b-2 extending into the front portion of the midsole from a top thereof, with the second upper flex groove 127 b-2 being vertically aligned with the second lower flex groove 127 b-1 so as to reduce a thickness of the midsole 120 therebetween (and thus promote flexibility between the wearer's big toe and the rest of the wearer's toes). The thickness of the midsole 120 may be reduced in this way to 20%-35% (preferably 25%-30% or 4-10 mm, for example) of a maximum thickness of the midsole 120, for example. The use of first and second longitudinal flex grooves 127 a, 127 b spaced apart in this way may effectively segment the front portion 122 of the midsole 120 into forefoot pods or segments, one supporting the 1st ray, one supporting the 2nd and 3rd rays, and one supporting the 4th and 5th rays. The longitudinal flex grooves 127 a, 127 b may allow each of the pods to move independent of one another, for example, by 2-10 mm vertically.

Owing to the combined toe spring and flexibility of the front portion 122 of the midsole 120, the disclosed running shoe 100 may allow the wearer's toes first to lift during the swing phase of the gait cycle according to the toes-up bias imparted by the toe spring (i.e., the “toe-up” position shown with broken lines in FIG. 3 ), pre-tensioning the musculature of the foot prior to impact with the ground, and then to lower in two or more distinct, accordion-like movements. When barefoot, the toes naturally do this in five distinct accordion-like movements (one per toe). By grouping the toes as described above using first and second longitudinal flex grooves 127 a, 127 b spaced apart from each other, the toes may lower in three movements, first the 4th and 5th toes, then the 2nd and 3rd toes, and last the 1st (big) toe, resulting in a similar effect that closely mirrors the natural biomechanics of the foot while running or walking barefoot. It is contemplated, however, that more (four or five) or fewer (two) groupings may be used. The disclosed running shoe 100 may advantageously make such individual movements of the toes possible within the confines of a cushioned shoe having a midsole 120 that cushions and supports the wearer's foot including the toes (unlike, for example, Vibram FiveFingers, sold by Vibram Corporation). Moreover, this may have the effect of creating distinct impact zones, much like the crumple zones in a car, each absorbing impact force separately without transferring it as quickly or directly to the other segments over a slightly lengthened period of time, thus dampening direct impact forces by spreading them out over a greater distance and period of time.

Preferably, a maximum width of the front portion 122 of the midsole 120 in the lateral to medial direction of the running shoe 100 may be large enough to allow the wearer's forefoot to freely splay or spread more than 10% (e.g., 15-20%) within the shoe, which the foot is designed to do while barefoot. For example, the maximum width of the front portion 122 may be greater than 140% (preferably greater than 150%) of a maximum width of the rear portion 124 of the midsole 120 in the lateral to medial direction of the running shoe 100. The maximum width of the front portion 122 may be, for example greater than 90 mm, preferably 100-110 mm, for a standard U.S. men's size 9D (with proportionally greater or less width for other sizes as noted above). The width of the midsole 120 may be measured at the top of the midsole 120, for example. By allowing the foot to splay unimpeded within the shoe 100 in one plane and due to the toes lowering in another direction toward the plane over a slightly longer period of time, the impact forces may be further dampened, further reducing the risk of injury and making for a more cushioned footstrike.

Referring now to FIGS. 4, 6, and 8 , the rear portion 124 of the midsole 120, corresponding to the heel of the wearer, may have a flat bottom 128 that is narrower than the upper 110 in the lateral to medial direction of the running shoe 100. As shown in FIG. 8 , which is a cross-sectional view taken along the line 8-8 in FIG. 5 , a width W_(B) of the flat bottom 128 may be less than a width W_(U) of the upper 110. For a standard U.S. men's size 9D, for example, the width W_(B) of the flat bottom 128 may be less than 65 mm at its widest (preferably less than 50 mm, with the corresponding width W_(U) of the upper 110 being greater than 60 mm), and with proportionally greater or smaller measurements being used for other sizes as explained above. As a result of W_(B) being less than W_(U), the flat bottom 128 may fall substantially underneath the wearer's heel, unlike conventional running shoes whose midsoles typically have a very wide rear portion that extends laterally and medially beyond the upper and thus beyond the actual heel of the wearer. Preferably, the flat bottom 128 may extend only so far as the actual flattened area of contact between the wearer's naturally round heel and the top of the midsole 120 or sockliner within the running shoe 100, effectively simulating the flattened area of contact that would occur were the naturally round heel of the wearer to press down on the ground directly.

The relationship W_(B)<W_(U) may be met along the entire flat bottom 128 of the rear portion 124 of the running shoe 100 at any given longitudinal position (i.e., in the front to back direction of the running shoe 100). The flat bottom 128 of the rear portion 124 may be rounded about a perimeter thereof as shown in FIG. 4 . For example, the rear portion 124 of the midsole 120 may be rounded from the lateral side 106 to the medial side 108 of the running shoe 100 around the back 104 thereof, and the perimeter of the flat bottom 128 may trace a corresponding curve therewithin. Toward the foremost part of the rear portion 124 of the midsole 120 (which may end about one-third of the way from the back 104 to the front 102 of the running shoe 100), the perimeter of the flat bottom 128 may close such that the flat bottom 128 takes on an egg shape as shown or other ovoid form, which may preferably correspond to the shape of the wearer's flattened heel within the shoe 100. Alternatively, the flat bottom 128 of the rear portion 124 of the midsole 120 may not end in the rear portion 124 as shown in FIG. 4 and may instead continue forward underneath the midfoot of the wearer, with the midsole 120 thus defining a connecting bridge that extends from the rear portion 124 to the front portion 122.

Referring again to FIG. 8 , the rear portion 124 of the midsole 120 may be rounded from the flat bottom 128 thereof to the lateral and medial sides 106, 108 of the running shoe 100 according to one or more radii of curvature R1, R2, which may be in the range of 15-25 mm, for example. It is contemplated that the lateral radius of curvature R1 may be the same as or different from the medial radius of curvature R2 at any given longitudinal position. The rear portion 124 of the midsole 120 may likewise be rounded from the flat bottom 128 thereof to the back 104 of the running shoe 100 according to a radius of curvature R3 (see FIG. 6 ), which may be the same as or different from either or both of the radii of curvature R1, R2. By defining such a substantial rounding between the flat bottom 128 and the sides 106, 108 and/or back 104 of the running shoe 100, the rear portion 124 of the disclosed midsole 120 (with optional outsole 130) may approximate the rounding of a person's heel.

Owing to the flat bottom 128 of the rear portion 124 of the midsole 120 being narrower than the upper 110, as well as the preferably substantial rounding between the flat bottom 128 and the sides 106, 108 and/or back 104 of the running shoe 100, the contact between the running shoe 100 and the ground may simulate the contact between a bare heel and the ground. This may result in various advantages, which may include a faster and smoother transition of impact forces and the body's center of mass from heel to forefoot through the ground contact phase of the gait cycle and/or reduced rotational torque applied to the foot and transferred to other lower limb joints from naturally occurring pronation (as opposed to the acceleration of naturally occurring pronation and torque forces from shoes with wider, significantly larger flat heel surfaces). The more efficient transfer of impact forces and the body's center of mass from heel to forefoot, coupled with the reduced rotational forces of the foot, may mitigate the forces created by running and walking, reducing the risk of injury in comparison with using conventional running shoes.

In combination, the unique design features of both the front portion 122 and the rear portion 124 of the midsole 120 described above may work together in concert to create a benefit of reduced impact and torque forces that is greater than the sum of each if accounted for independent of one another. The features of the front portion 122 may feed the features of the rear portion 124 and vice versa in successively greater step-downs of impact forces and torque, resulting in a composite reduction of forces that cannot be otherwise achieved.

Throughout the above disclosure, various example measurements are provided for a U.S. men's size 9D with the explanation that the measurements may be greater or less according to conventional shoe sizing algorithms. By way of further example, the following Table 1 shows selected last measurements of a last that may be used to produce the disclosed running shoe 100. The Size column reflects standard U.S. men's shoe sizes, while all other measurements are in millimeters.

TABLE 1 Stick Bottom Bottom Heel Toe Size Length Length Width Width Spring 3.5 221.16 232.74 94.6 53.8 47.62 4 225.39 236.97 95.6 54.4 48.29 4.5 229.62 241.20 96.7 55.0 48.96 5 233.85 245.43 97.7 55.6 49.63 5.5 238.08 249.66 98.8 56.2 50.30 6 242.31 253.89 99.9 56.8 50.97 6.5 246.54 258.12 100.9 57.5 51.65 7 250.77 262.35 102.0 58.1 52.32 7.5 255.00 266.58 103.0 58.7 52.99 8 259.23 270.81 104.1 59.3 53.66 8.5 263.46 275.04 105.2 59.9 54.33 9 267.69 279.27 106.2 60.5 55.0 9.5 271.92 283.50 107.3 61.1 55.67 10 276.15 287.73 108.3 61.7 56.34 10.5 280.38 291.96 109.4 62.3 57.01 11 284.61 296.19 110.5 62.9 57.68 11.5 288.84 300.42 111.5 63.5 58.36 12 293.07 304.65 112.6 64.1 59.03 12.5 297.30 308.88 113.6 64.7 59.70 13 310.53 313.11 114.7 65.3 60.37 13.5 305.76 317.34 115.8 65.9 61.04 14 309.99 321.57 116.8 66.5 61.71 14.5 314.22 325.80 117.9 67.1 62.38 15 318.45 330.03 118.9 67.7 63.05 15.5 322.68 334.26 120.0 68.3 63.72 16 326.91 338.49 121.1 68.9 64.39 16.5 331.14 342.72 122.1 69.5 65.07 17 335.37 346.95 123.2 70.1 65.74 17.5 339.60 351.18 124.2 70.7 66.41 18 343.83 355.41 125.3 71.3 67.08

As noted above, the midsole 120 of the running shoe 100 may exhibit zero drop from the rear portion 124 all the way to the foremost point 123 described above. As such, the midsole 120 may have a consistent thickness instead of tapering in the region of the wearer's toes. As a result, the toe spring measurements of the last, as exemplified in Table 1, may match the toe spring measurements of the finishing running shoe 100 that includes the midsole 120. Accordingly, another aspect of the embodiments of the present disclosure is a last for manufacturing a running shoe, the last defining a toe spring of at least 40 mm, preferably at least 50 mm. The last may be used to produce the upper 110, with the disclosed midsole 120, outsole 130, etc. being attached thereto to produce a running shoe 100 as described herein.

Referring now to FIGS. 9-16 , another running shoe 200 is shown illustrating various features of a midsole 220 thereof that may replace or be combined with the features of the midsole 120 described above. This running shoe 200 may be the same as the running shoe 100 and may have a midsole 220 and outsole 230 that are the same as the midsole 120 and outsole 130 of the running shoe 110, with the midsole 220 having a front portion 222, rear portion 224, flex grooves 226 a, 226 b, 227 a, 227 b, and flat bottom 228 that are the same as the front portion 122, rear portion 124, flex grooves 126 a, 126 b, 127 a, 127 b, and flat bottom 128, except as described herein. As will be detailed and elaborated upon, the running shoe 200 may have a unique midsole 220 and outsole 230 as well as channels 204, notches 202, and void regions 208 that may serve to improve the flexibility and movability of the running shoe 200, particularly the midsole 220 of the running shoe 200.

Turning first to FIGS. 9-12 , views of this running shoe 200 are shown, with FIG. 11 showing a front view of the unique midsole 220 and FIG. 12 outlining how the upper 110 may fit into the midsole 220. It can be seen in this running shoe 200 that the midsole 220 may have one or more notches 202. As will be shown, these notches 202 may allow the flexibility of the running shoe 200, particularly that of the midsole 220, to be increased. The notches 202 may be present in the front portion 222 of the midsole 220 in a sidewall 229 thereof. Specifically, the notches 202 may be in a top rail 231 of the midsole 220 that defines a portion of the sidewall 229. Five notches 202 are present on the lateral side 106, medial side 108, and the front 102 of the running shoe 200 shown in these FIGS. 9-12 , although the notches 202 need not be limited to the number and the particular position depicted therein. The notches 202 need not be of the square/rectangular shape depicted in FIGS. 9-12 , as they can be any shape, including round, triangular, etc. A notch 202 may increase the flexibility of the midsole 220, for example, by allowing the midsole 220 to more easily expand and contract about the notch 202. In other words, the midsole 220 may be allowed to more easily pinch and widen about a notch 202. This mechanism may be advantageously used alongside the aforementioned toe spring, in which the enhanced flexibility of the midsole 220 may allow the front portion 222 of the midsole 220 to lie flat in response to an even lesser amount of applied force. A notch 202 may be formed by removing (such as by cutting out) the material of the midsole 220. Alternatively, the midsole 220 may be manufactured so that the material of the midsole 220 is molded to include the notch 202.

Another feature of this running shoe 200, which may be beneficially associated with the notches 202, are the flex grooves 226, 227. Similar to the flex grooves 126, 127 of the previously discussed running shoe 100, this running shoe may have one or more horizontal flex grooves 226 and one or more longitudinal flex grooves 227. In FIGS. 9-12 , it can be recognized that the lower flex grooves 226 a-1, 226 b-1, 227 a-1, 227 b-1 may extend through the edge of the midsole 220 of the running shoe 200, that is, all the way through the sidewall 229. While only the lower flex grooves 226 a-1, 226 b-1, 227 a-1, 227 b-1 extend through the edge of the midsole 220 in this manner in this running shoe 200, it is contemplated that one or more of the upper flex grooves 226 a-2, 226 b-2, 227 a-2, 227 b-2 may also or alternatively extend through the edge of the midsole 220. However, in order to provide an adequate surface for gluing or otherwise attaching the upper 230 to the midsole 220, the upper flex grooves 226 a-2, 226 b-2, 227 a-2, 227 b-2 may stop short of reaching the edge of the midsole 220, as shown in FIG. 14 . By virtue of the notches 202 being formed in the top rail 231 of the midsole 220 in alignment with the flex grooves 226 a-2, 226 b-2, 227 a-2, 227 b-2, a high degree of flexibility may still be achieved despite the termination of the flex grooves 226 a-2, 226 b-2, 227 a-2, 227 b-2 prior to the edge of the midsole 220. While all the lower flex grooves 226 a-1, 226 b-1, 227 a-1, 227 b-1 present in the running shoe 200 extend through the midsole 220 as is the case in FIGS. 9-12 , a running shoe 220 may have a combination of flex grooves 226, 227 that extend through the edge of the midsole 220 and flex grooves 226, 227 that do not. Similar to the notches 202, the extension of a flex groove 226, 227 through the edge of the midsole 220 may allow for the flexibility of the midsole 220 to be increased, one mechanism of which could be by allowing the midsole 220 to expand and contract about the space in the midsole 220 associated with the extension of the flex groove 226, 227 with greater ease.

A flex groove 226, 227 which extends through the edge of the midsole 220 may be associated with a notch 202 in the midsole 202 via a channel 204. A channel 204 may be a vertical channel which may extend from a top to bottom direction of the running shoe 200. In this respect, the channels 204 may extend straight in the top to bottom direction of the running shoe 200, diagonally across this up and down direction, or a combination thereof (i.e., portions of the channel that are straight and portions of the channel that are diagonal). The channels 204 may act as an indentation or recess in the midsole 220 extending inward towards the wearer's foot. These FIGS. 9-12 show channels 204 that have sharp edges which break the continuity of the midsole 220, but the channels 204 need not have sharp edges in this manner, as these edges can be beveled or smooth and continuous with the rest of the midsole 220 such that the material of the midsole 220 may smoothly transition to a channel 204. A channel 204 may also have a combination of smooth and sharp edges.

The channels 204 may define a channel width extending along the side (lateral 106 and/or medial 108) of the running shoe 200, a channel height extending between the top and bottom of the running shoe 200, and a channel depth extending inwards and towards the wearer's foot, all of which need not be consistent across a particular dimension (e.g., it can be seen in these FIGS. 9-12 that the channel depth may vary across the channel height). These channel dimensions, and geometry of the channels 204 that may result from those dimensions, may at least partially define one or more channel surfaces. The channel surfaces may be the portions of the midsole 220 that are associated with the indentation/recess of the channel 204. For example, the channels 204 in these FIGS. 9-12 , illustrating one example geometry, are rectangular and can thus define three channel surfaces: two side channel surfaces 206 approximately opposite to each other and both at least partially defined by the channel depth, as well as a base channel surface 210 therebetween that is at least partially defined by the channel width and the channel height. However, it is contemplated that a channel 204 may form a different geometry that may define more than three surfaces or less than three surfaces. Examples include channel(s) 204 being triangular and defining two channel surfaces, or channel(s) 204 being more circular and having one, curved channel surface. Various shapes and structures, including abstract variations and patterns, may therefore be implemented into the geometry of the channels 204. The channel surfaces may be distinguishable from one another via sharp edges between different channel surfaces (such as in the case of the rectangular channels in FIGS. 9-12 ).

A channel 204 need not necessarily be associated with any notches 202 or flex grooves 226, 227, but in the case of the illustrated running shoe 200 of FIGS. 9-12 , each channel 204 present is associated with both a notch 202 and a flex groove 226, 227. Alternatively, a channel 204 may be associated with just one of a notch 202 or a flex groove 226, 227. The channels 204 may terminate (in the vertical direction) in one or more notches 202 defined in the midsole 220 in the top (via a notch 202 in the top rail 231, for instance) and/or bottom surface thereof. These notches 202 may further define one or more of the aforementioned channel surfaces. As it can be seen in FIGS. 9-12 , the base channel surfaces 210 of each of the channels 204 is partially defined by a notch 202. There need not be just one notch 202 that helps to define just one channel surface, as there could be more than two notches 202 associated with one channel 204. More than one channel surfaces of the channels 204 may be at least partially defined by one or more of these notches 202, although in FIGS. 9-12 , only the base channel surface 210, and not the side channel surfaces 206, is partially defined in this aspect. A notch 202 in the top rail 231 of the midsole 220 may expose a portion of the upper 110 of the running shoe 200 as shown.

Similarly flex groove 226, 227 may be associated with a channel 204 via the flex groove 226, 227 extending through the edge of the midsole 220 at a channel 204 (that being the case for each of the flex grooves 226, 227 in FIGS. 9-12 ). As in the case of the notches 202, the flex groove 226, 227 may help to define one or more of channel surfaces. A flex groove 226, 227 may extend through the edge of the midsole 220 once at one channel 204 or more than once throughout multiple channels 204. In the running shoe 200 of FIGS. 9-12 , it can be seen that the horizontal flex grooves 226 may each extend through the edge of the midsole 220 twice at two channels 204, while the longitudinal flex grooves 227 may each extend through the midsole 220 once at one channel 204.

It can be seen that a notch 202 and a flex groove 226, 227 that extends through the edge of the midsole may both be associated with one another via a channel 204 (as is the case for every notch 202 and flex groove 226, 227 in FIGS. 9-12 ). This association may result in a synergistic effect in which the midsole 220 may more easily bend, expand, and/or contract about the notch 202 and flex groove 226, 227, thus increasing the flexibility of the midsole 220 even further. Therefore, a wearer's foot could move in its natural range of motion with enhanced comfort and ease while wearing this running shoe 200.

Referring now to FIGS. 13 and 14 , a top and bottom view respectively of the midsole of the running shoe 200 are shown. Another feature depicted here in this running shoe 200 is the presence of void regions 208 which may span the flex grooves 226, 227. These void regions 208 may extend entirely from a top to bottom direction of the midsole 220 such that the void regions 208 may define a void in those particular regions of the midsole 220 and the flex grooves 226, 227. In other words, the thickness of the midsole 220 may be reduced to zero in those void regions 208. The void regions 208 may span at least a portion of the flex grooves 226, 227, and as such the void regions 208 may span a greater portion or a lesser portion of the flex grooves 226, 227 when compared to the depiction shown by way of example in FIGS. 13 and 14 . Additionally, there need not be only two void regions 208, as there could be just one void region 208 or more than two void regions 208. It can also be seen in these FIGS. 13 and 14 that a void region 208 may span both a horizontal flex groove 226-a and a longitudinal flex groove 227 a, 227 b, which may be particularly advantageous in increasing the flexibility and moveability for the forefoot pods, as will be described next. It is contemplated that a void region 208 can span any number and combination of flex grooves 226, 227, meaning that the void regions 208 are not limited to how they are depicted in FIGS. 13 and 14 .

Looking momentarily now to FIGS. 15 and 16 , cross sectional views along lines 15-15 and 16-16 of FIG. 14 of this running shoe are shown. In these figures, the architectures of the flex grooves 226, 227, the void regions 208, and the association between the two are more clearly shown. Outside of the void regions 208, the thickness of the midsole 250 is non-zero and still reduced in between the flex grooves 226 a-1, 226 a-2, and 226 b-1, 226 b-2, while the portions of the flex grooves 226, 227 that have void regions 208 define voids where no material of the midsole 220 is present.

Turning back now to FIGS. 13 and 14 , the benefits the void regions 208 may yield to the running shoe 200 will be detailed. These void regions 208 may add to the flexibility of the midsole 220 and outsole 230 of the running shoe 200, one mechanism being via increasing the movability of one or more of the forefoot pods defined by an intersecting and extending relationship between the flex grooves 226, 227 to be described next. A flex groove 226, 227 may intersect one or more different flex grooves 226, 227 at an intersection point 280. For example, a horizontal flex groove 226 may intersect a longitudinal flex groove 227 at an intersection point 280. This can be seen in FIGS. 13 and 14 , where both the horizontal flex grooves 226 a, 226 b intersect both the longitudinal flex grooves 227 a, 227 b about four different intersection points 280. Furthermore, a flex groove 226, 227 may extend through an intersection point 280 if that flex groove 226, 227 continues to travel through and past that intersection point 280. Looking to the depiction of FIGS. 13 and 14 , the longitudinal flex grooves 227 a, 227 b both extend through the first horizontal flex groove 226 a through their respective intersection points 280, and both of the horizontal flex grooves 226 a, 226 b extend through both of the longitudinal flex grooves 227 a, 227 b across all four of the intersection points 280. This intersecting and extending relationship between any flex grooves 226, 227 of the running shoe 200 may define forefoot pods which may reside in between the flex grooves 226, 227. Specifically in FIGS. 13 and 14 , these relationships have resulted in the running shoe 200 having a back medial forefoot pod 282, a back intermediate forefoot pod 286, a back lateral forefoot pod 284, a front medial forefoot pod 288, a front intermediate forefoot pod 290, and a front lateral forefoot pod 292. As mentioned earlier, the forefoot pods may be movable independent of one another.

The void regions 208 may be operative to increase the movability of the forefoot pods of the running shoe 200. The discontinuity of the midsole 220 defined by the void region 208 in between the forefoot pods may allow those forefoot pods 282, 284, 286, 288, 290, 292 to move in the up and down direction of the midsole 220 with greater ease. Generally, the closer a void region 208 is to a forefoot pod 282, 284, 286, 288, 290, 292, the more that void region 208 may be able to increase the movability to that forefoot pod 282, 284, 286, 288, 290, 292. A void region 208 that spans a greater region of the flex groove 226, 227 may be more effectual at increasing the movability of the forefoot pods 282, 284, 286, 288, 290, 292. In the case of FIGS. 13 and 14 , the back medial forefoot pod 282 and the back lateral forefoot pod 284 may have a particularly increased movability when compared to the rest of the forefoot pods 286, 288, 290, 292 via their spatial relationship with the void regions 208. This is achieved via the void region 208 on the medial side 108 of the running shoe 200 (which may be referred to as a medial void region) spanning a portion of the first horizontal flex groove 226 a between the back medial forefoot pod 282 and the front medial forefoot pod 288 as well as a portion of the second longitudinal flex groove 227 b between the back medial forefoot pod 282 and the back intermediate forefoot pod 286, resulting in greater movability and flexibility of the back medial forefoot pod 282. Similarly, the void region 208 on the lateral side 106 of the running shoe 200 (which may be referred to as a lateral void region) spans a portion of the first horizontal flex groove 226 a between the back lateral forefoot pod 284 and the front lateral forefoot pod 292 as well as a portion of the first longitudinal flex groove 227 a between the back lateral forefoot pod 284 and the back intermediate forefoot pod 286 to attain greater movability and flexibility of the back lateral forefoot pod 284.

If forefoot pods are correlated to particular metatarsal heads of a wearer's foot, the forefoot pods may be operative to allow for those particular metatarsal heads to independently move up and down within the running shoe 200. In the example of FIGS. 13 and 14 , the back medial forefoot pod 282 may correspond to the 1^(st) metatarsal head of a wearer's foot while the back lateral forefoot pod 284 may correspond to the 4^(th) and 5^(th) metatarsal heads of a wearer's foot, with these three metatarsal heads being the ones that move the most during the natural movement of a wearer's foot while walking/running. This construction of the running shoe 200 may allow for the metatarsal heads to move up and down as they naturally would while running/walking while still being contained in the running shoe 200. This may thus enable one to move more freely and comfortably, allowing for a more natural and pleasant movement of a wearer's foot.

It is contemplated that numerous different arrangements of the flex grooves 226, 227 resulting in unique forefoot pods as well as the void regions 208 that may span those flex grooves 226, 227 could be configured and implemented so as to produce different running shoes that have different levels of flexibility and moveability of the midsole 220 and any forefoot pod. For example, a single horizontal flex groove may intersect and extend through a single longitudinal flex groove to define two forefoot pods in front of the horizontal flex groove, a lateral forefoot pod on the lateral side of the running shoe and a medial forefoot pod on the medial side of the running shoe. Another shoe may modify this design to include a second horizontal flex groove which intersects with the first longitudinal flex groove to now define four forefoot pods, a front medial forefoot pod, a back medial forefoot pod, a front lateral forefoot pod, and a back lateral forefoot pod. Any of these running shoes can incorporate void regions to increase the flexibility of forefoot pods, with particular void region geometries being operative to increase the flexibility of certain forefoot pods more than others.

The above description is given by way of example, and not limitation. Given the above disclosure, one skilled in the art could devise variations that are within the scope and spirit of the invention disclosed herein. Further, the various features of the embodiments disclosed herein can be used alone, or in varying combinations with each other and are not intended to be limited to the specific combination described herein. Thus, the scope of the claims is not to be limited by the illustrated embodiments. 

What is claimed is:
 1. A running shoe comprising: an upper; and a midsole attached to the upper, the midsole having a front portion corresponding to a forefoot and a rear portion corresponding to a heel, the front portion of the midsole defining a plurality of flex grooves including one or more horizontal flex grooves and one or more longitudinal flex grooves, the one or more horizontal flex grooves extending in a lateral to medial direction of the running shoe, the one or more longitudinal flex grooves extending in a front to back direction of the running shoe, the front portion of the midsole having one or more notches formed in a top rail thereof, the one or more notches being operative to increase the flexibility of the midsole.
 2. The running shoe of claim 1, wherein the front portion of the midsole further has one or more channels, the one or more channels extending vertically in a top to bottom direction of the running shoe, the one or more channels each defining at least one channel surface.
 3. The running shoe of claim 2, wherein each of the one or more channels is rectangular and has three channel surfaces, the three channel surfaces being two side channel surfaces approximately opposite to each other and a base channel surface therebetween.
 4. The running shoe of claim 2, wherein at least one of the one or more channels is associated with a notch from among the one or more notches, the notch further defining at least one of the channel surfaces of the at least one channel.
 5. The running shoe of claim 2, wherein at least one of the plurality of flex grooves is associated with at least one of the one or more channels.
 6. The running shoe of claim 2, wherein at least one of the one or more horizontal flex grooves is associated with at least two of the one or more channels.
 7. The running shoe of claim 6, wherein at least one of the one or more longitudinal flex grooves is associated with at least one of the one or more channels.
 8. The running shoe of claim 2, wherein at least one of the one or more notches and at least one of the plurality of flex grooves are associated with one of the one or more channels.
 9. A running shoe comprising: an upper; and a midsole attached to the upper, the midsole having a front portion corresponding to a forefoot and a rear portion corresponding to a heel, the front portion of the midsole defining a plurality of flex grooves including one or more horizontal flex grooves and one or more longitudinal flex grooves, the one or more horizontal flex grooves extending in a lateral to medial direction of the running shoe, the one or more longitudinal flex grooves extending in a front to back direction of the running shoe, at least a portion of at least one of the plurality of flex grooves extending entirely through the midsole to define one or more voids in the midsole.
 10. The running shoe of claim 9, wherein the at least a portion of the at least one flex groove that extends entirely through the midsole spans at least a portion of at least one of the one or more horizontal flex grooves and at least a portion of at least one of the one or more longitudinal flex grooves.
 11. The running shoe of claim 9, wherein the one or more horizontal flex grooves includes at least one horizontal flex groove that intersects at least one of the one or more longitudinal flex grooves to define one or more forefoot pods, the one or more forefoot pods being movable independent of one another; and wherein the at least a portion of the at least one flex groove that extends entirely through the midsole spans at least a portion of the at least one horizontal flex groove and at least a portion of the at least one longitudinal flex groove.
 12. The running shoe of claim 9, wherein the one or more horizontal flex grooves includes at least one horizontal flex groove that extends through at least one of the one or more longitudinal flex grooves to define two or more forefoot pods, the two or more forefoot pods being movable independent of one another.
 13. The running shoe of claim 12, wherein the two or more forefoot pods includes a medial forefoot pod and a lateral forefoot pod; and wherein the at least a portion of the at least one flex groove that extends entirely through the midsole spans at least a portion of the at least one horizontal flex groove and at least a portion of the at least one of the one or more longitudinal flex grooves.
 14. The running shoe of claim 9, wherein the one or more horizontal flex grooves includes a front horizontal flex groove and a back horizontal flex groove spaced from each other in the front to back direction of the running shoe, the front horizontal flex groove and the back horizontal flex groove extending through at least one of the one or more longitudinal flex grooves and the at least one of the one or more longitudinal flex grooves extending through the front horizontal flex groove to define four or more forefoot pods, the four or more forefoot pods being movable independent of one another.
 15. The running shoe of claim 14, wherein the four or more forefoot pods includes a front lateral forefoot pod, a back lateral forefoot pod, a front medial forefoot pod, and a back medial forefoot pod all being moveable independent of one another; and wherein the at least a portion of the at least one flex groove that extends entirely through the midsole spans at least a portion of the at least one of the one or more longitudinal flex grooves and at least a portion of the back horizontal flex groove.
 16. The running shoe of claim 9, wherein the one or more horizontal flex grooves includes a front horizontal flex groove and a back horizontal flex groove spaced from each other in the front to back direction of the running shoe, the one or more longitudinal flex grooves including a lateral longitudinal flex groove and a medial longitudinal flex groove spaced from each other in the lateral to medial direction of the running shoe, the front horizontal flex groove and the back horizontal flex groove extending through at least the lateral longitudinal flex groove and the medial longitudinal flex groove, the lateral longitudinal flex groove and the medial longitudinal flex groove extending through at least the front horizontal flex groove to define six or more forefoot pods.
 17. The running shoe of claim 16, wherein the six or more forefoot pods includes a front lateral forefoot pod, a back lateral forefoot pod, a front medial forefoot pod, a back medial forefoot pod, a front intermediate forefoot pod, and a back intermediate forefoot pod all being movable independent of one another; and wherein the at least a portion of the at least one flex groove that extends entirely through the midsole includes a portion that spans at least a portion of the back horizontal flex groove and at least a portion of the lateral longitudinal flex groove and a portion that spans at least a portion of the back horizontal flex groove and at least a portion of the medial longitudinal flex groove.
 18. The running shoe of claim 17, wherein the portion that spans at least a portion of the back horizontal flex groove and at least a portion of the lateral longitudinal flex groove is operative to increase the movability of the back lateral forefoot pod; and wherein the portion that spans at least a portion of the back horizontal flex groove and at least a portion of the medial longitudinal flex groove is operative to increase the movability of the back medial forefoot pod.
 19. A running shoe comprising: an upper; and a midsole attached to the upper, the midsole having a front portion corresponding to a forefoot and a rear portion corresponding to a heel, the front portion of the midsole defining a plurality of flex grooves including one or more horizontal flex grooves and one or more longitudinal flex grooves, the one or more horizontal flex grooves extending in a lateral to medial direction of the running shoe, the one or more longitudinal flex grooves extending in a front to back direction of the running shoe, the front portion of the midsole having one or more notches formed in a top rail thereof, the one or more notches being operative to increase the flexibility of the midsole, at least a portion of at least one of the plurality of flex grooves extending entirely through the midsole to define one or more voids in the midsole.
 20. The running shoe of claim 19, wherein the front portion of the midsole further has one or more channels, the one or more channels extending vertically in a top to bottom direction of the running shoe, the one or more channels each defining at least one channel surface; and wherein each of the plurality of flex grooves is associated with at least one of the one or more channels; and wherein each of the one or more notches are associated with at least one of the one or more channels. 